The present invention relates generally to a method and apparatus for setting a sidetrack plug in a well bore. More particularly but not by way of limitation, the invention relates to a bottom hole tool which utilizes an inflation packer to set hydrostatically balanced or unbalanced kickoff plugs for altering the direction of a well bore.
During the drilling of a well, it is often necessary, for various reasons, to alter the direction of the well bore. One way to alter the well direction is to set a whipstock in a well bore. A whipstock has an inclined ramp or guide surface at its upper end. The whipstock may be placed in the well on top of a packer, and the direction of the well may be altered by directing a drill bit into the side of a well bore with the inclined ramp.
It is also well known that a column of cementitious fluid placed in a well bore is useful as a sidetrack or kickoff plug for altering the direction of the well bore as it is being drilled. Such plugs may be either hydrostatically balanced or unbalanced. Once the sidetrack plug is set in the well bore, a drill bit can drill into the plug and into the side of the well bore to alter the direction of the well bore. There are however, difficulties associated with setting such plugs.
Sidetrack plugs are presently set by lowering an open ended tubing string into a well bore to the desired depth of the plug. A cementitious fluid is pumped through the tubing string and out the open end of the tubing string. The pressure in the well bore forces the cementitious fluid up the annulus between the tubing string and the well bore. The cementitious fluid is continually displaced until a kickoff plug of a desired length is set. The tubing is then removed from the hole and the cementitious fluid is allowed to gel and harden. As the tubing is pulled from the cementitious fluid, however, a vacuum or suction is created in the fluid which can often contaminate the kickoff plug by drawing debris from the well bore into the cementitious fluid. Such contamination affects the integrity of the plug. Thus, such a method often does not allow successful sidetrack drilling to begin on the first attempt. The industry range for obtaining a successful sidetrack using such a plug is 2 to 4 attempts.